[PATCH v2] MM: check limit while deallocating bootmem node

[Gavin Shan <shangw@linux.vnet.ibm.com>]

For the particular bootmem node, the minimal and maximal PFN (
Page Frame Number) have been traced in the instance of "struct
bootmem_data_t". On current implementation, the maximal PFN isn't
checked while deallocating a bunch (BITS_PER_LONG) of page frames.
So the current implementation won't work if the maximal PFN isn't
aligned with BITS_PER_LONG.

The patch will check the maximal PFN of the given bootmem node.
Also, we needn't check all the bits map when the starting PFN isn't
BITS_PER_LONG aligned. Actually, we should start from the offset
of the bits map, which indicated by the starting PFN. By the way,
V2 patch removed the duplicate check according to comments from
Johannes Weiner.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
---
 mm/bootmem.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/bootmem.c b/mm/bootmem.c
index 5a04536..b4f3ba5 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -201,9 +201,11 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 			count += BITS_PER_LONG;
 			start += BITS_PER_LONG;
 		} else {
-			unsigned long off = 0;
+			unsigned long cursor = start;
+			unsigned long off = cursor & (BITS_PER_LONG - 1);
 
-			while (vec && off < BITS_PER_LONG) {
+			vec >>= off;
+			while (vec) {
 				if (vec & 1) {
 					page = pfn_to_page(start + off);
 					__free_pages_bootmem(page, 0);
@@ -211,6 +213,7 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 				}
 				vec >>= 1;
 				off++;
+				cursor++;
 			}
 			start = ALIGN(start + 1, BITS_PER_LONG);
 		}
-- 
1.7.5.4

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